Did you hate your mom as a teenager? Who didn't! But a negative relationship between mothers and daughters taken in tandem with low serotonin levels could lead to cutting and other self-harm, a new study shows. Fraught mother/daughter dealings alone generally do not inspire cutting, says study co-author, University of Washington psych professor Theodore Beauchaine. It's the combo of low serotonin ("an important chemical for brain stability," says Science Daily) and poor mother/daughter relations that's really the one-two punch. "Most people think in terms of biology or environment rather than biology and environment working together," says Beauchaine. "Having a low level of serotonin is a biological vulnerability for self-harming behavior and that vulnerability increases remarkably when it is paired with maternal conflict."

How bad does a relationship have to be to get branded as "negative"? The researchers at the University of Washington chose a topic that both parent and child said was a "serious issue." The most common area of conflict was chores. Mother and child then discussed the sticky subject for 10 minutes, while assistants recorded and coded the conversation. According to Beauchaine, "You would think that they would be civil to each other in this kind of situation, but many of these topics were hot and within five minutes some of our subjects were arguing with each other."

"Once self-harming behavior starts it is difficult to stop," Beauchaine added, "So you want to prevent this behavior before it starts." But is every parent of a troubled girl supposed to get her serotonin levels checked just in case the young woman might start up with a razor? That doesn't sound practical. Lots of mothers and daughters have arduous relationships: how can you know when it's veering into truly dangerous territory?